WASHINGTON (AP), May 02- Florida Republican Sen. Marco Rubio says a new immigration bill he helped write, needs stronger border security provisions or it will fail in the House and may even have trouble getting through the Senate.

Rubio, who is the chief emissary to conservatives on the contentious legislation, said in a radio interview and in an opinion piece being published in Friday's Wall Street Journal that he's been hearing concerns in recent days that more work is needed to boost the bill's language on the border and he said he's committed to trying to make those changes.

In his Wall Street Journal piece, Rubio cited ``triggers'' in the bill that aim to make new citizenship provisions contingent on border security accomplishments. Critics say those provisions are too weak, because in some cases the Homeland Security secretary is tasked with undertaking studies - but not with delivering results - before millions in the U.S. illegally can obtain legal status.

Rubio also mentioned revisiting ``waivers'' in the bill that give federal officials discretion in applying the law, another flashpoint for conservative critics; concerns about the bill's cost; and the possibility of making legalization provisions for immigrants already here ``tougher, yet still realistic.'' He didn't offer details.

``Clearly what we have in there now is not good enough for too many people and so we've got to make it better. And that's what I'm asking for and that's what we're working on,'' Rubio said separately this week in an interview with ``The Sean Hannity Show'' radio program.

``This bill will not pass the House and, quite frankly, I think, may struggle to pass the Senate if it doesn't deal with that issue, so we've got some work to do on that front,'' he said.

Rubio's comments came during Congress' one-week recess. Back home, lawmakers are hearing feedback about the 844-page bill. Rubio and seven Democratic and Republican senators - the so-called Gang of Eight - introduced the legislation April 17. The Senate Judiciary Committee is expected to begin voting on it next week.

In addition to improving border security, the bill would create new visa programs to bring many more foreign workers into the U.S., require employers to check their workers' legal status, and create a new pathway to citizenship for the 11 million immigrants living here illegally.

The bill faces a tough road in the Democratic-led Senate and an even tougher one in the GOP-controlled House, and some supporters say it will only be successful if Republicans believe it does enough on the border.

The Homeland Security Department would have six months to create a new border security plan to achieve the 90 percent effectiveness rate. Also within six months, the department would have to create a plan to identify where new fencing is needed. Once that happens, people living here illegally could begin to apply for a provisional legal status.

If the 90 percent rate isn't achieved within five years, a commission made of border state officials would make recommendations on how to do it.

After 10 years, people with provisional legal status could apply for permanent residency if the new security and fencing plans are operating, a new mandatory employment verification system is in place, and a new electronic exit system is tracking who leaves the country.

Critics say these triggers don't do enough.

``The triggers aren't triggers at all,'' Sen. Jeff Sessions, R-Ala., said in a statement. ``The day the bill passes, there will be an effective amnesty for the vast majority of illegal immigrants - abandoning the Gang of Eight's public promise of enforcement first.''

But changes aimed at strengthening the border security provisions could cause heartburn among Democrats. Advocates and the Obama administration have been reluctant to see citizenship made contingent on border security. Immigrants here illegally already face a 13-year path to citizenship under the bill - which Rubio said actually could stretch to as many as 20 years for some, given how long it takes to undertake certain steps - and anything that could make it more onerous raises concerns with supporters on the left.

The border security agreement is ``a very fragile and delicately worded part of the bill,'' said Angela Kelley, vice president for immigration policy at the liberal Center for American Progress. ``To me it really goes to the fundamental question of workability.''

Border security is just one issue that's likely to provoke a fight. There's also a brewing dispute over whether the bill should recognize gay unions so that gays could sponsor their partners to come to the U.S. Gay groups are pushing for an amendment in the Judiciary Committee to allow that, but Rubio and other Republicans have made clear it would cost their support.

White House press secretary Jay Carney was asked about the gay immigration issue on Air Force One en route to Mexico City on Thursday. ``We have said that we support that provision, but we also think it's very important to recognize that the overall bill here accomplishes what the president believes needs to be accomplished,'' Carney said.